Polysiloxane composition useful as a brake fluid

ABSTRACT

R-(OCnH2n)z-, -R&#39;&#39;-OH, and -Rs(OH)s, where Rs is a polyvalent hydrocarbon radical having s number of hydroxyl groups, where s varies from 2 to 5, n is a whole number that varies from 2 to 4, and z varies from 1 to 4, where a varies from 1.11 to 2.02, b varies from 0.023 to 1.00 and the sum of a + b varies from 2.024 to 3.00. The present invention also comprises a brake fluid system using the above polysiloxane polymer as the brake fluid.   WHERE R is a monovalent hydrocarbon radical or a halogenated monovalent hydrocarbon radical, R&#39;&#39; is a divalent hydrocarbon radical, E is selected from the group consisting of R-, ROR&#39;&#39;-,   A silicone polymer useful as brake fluid comprising a polymer of the structure,

United States Patent [1 1 Traver I POLYSILOXANE COMPOSITION USEFUL AS A BRAKE FLUID I75I Inventor: Frank .I. Traver, Troy. N.Y.

I73] Assignee: General Electric Company,

Waterford, NY.

I I Filed: Mar. I7, I971 IZII App]. No: 125,398

[52] CS. CI. 260/4481 B, 252/78, 60/548, 260/398. 260/4l0, 260/4109 R ISII Int. Cl. C07f 7/08 I58] Field of Search 60/52, 54.6, 548; 260/4109, 448.2 B, 398; 252/78 [56] References Cited UNITED STATES PATENTS 2,282,472 5/1942 Herman ct zll. 60/546 2.883.830 4/l959 Stelzer 60/52 2.902.829 9/[959 Verbrugge 60/52 3412.333 ll/l963 Bailey 260/4482 B 1 18.84 5/1967 Bluestein 260/4482 B X Primary Examiner-Paul F. Shaver Allorne). Agent. or Firm-Donald J. Voss; E. Philip Koltos; Frank L. Neuhauser l Jan.7,l975

I57] ABSTRACT A silicone polymer useful brake fluid comprising a polymer of the structure,

where R is a monovalent hydrocarbon radical or a halogenated monovalent hydrocarbon radical, R is a divalent hydrocarbon radical, E is selected from the group consisting of R, ROR-,

R(OC,,H R'OH, and -R-(OH),, where R is a polyvalent hydrocarbon radical having s num ber of hydroxyl groups, where s varies from 2 to 5, n is a whole number that varies from 2 to 4, and z varies from 1 to 4, where a varies from L! l to 2.02, b varies from 0.023 to L00 and the sum of a b varies from 2.024 to 3.00. The present invention also comprises a brake fluid system using the above polysiloxane polymer as the brake fluid. I

6 Claims, N0 Drawings POLYSILOXANE COMPOSITION USEFUL AS A BRAKE FLUID BACKGROUND OF THE INVENTION This invention relates to polysiloxane polymers and, in particular, this invention relates to ester polysiloxane polymers useful'as brake fluids.

It is desirable that a fluid which is to be used as a brake fluid meet certain performance criteria as well as certain suggested criteria for safety purposes, that is, the brake fluid must be such so that the brakes will operate efficiently and failure of the brakes will not result. These criteria must be met if the brake fluid is to be incorporated into new automobiles or if it is to be sold in the market in containers as brake fluid to be used on automobiles. The suggested criteria which a brake fluid must meet encompass an original equilibrium reflux boiling point determination, a wet equilibrium reflux boiling point determination, flash point determination, kinematic viscosity determination, pH value, brake fluid stability which encompasses high temperature stability and chemical stability, a corrosion determination, evaporation determination, water tolerance determination at low temperatures and at 60C, compatibility determination at low temperatures, a resistance to oxidation determination, effects on rubber determination and stroking property determination. The original equilibrium reflux boiling point determination is desired in order to determine that the brake fluid have a sufficiently high boiling temperature so that it will not boil at operating temperatures to which the brake fluid is subjected through the normal operation of the vehicle. It can easily be seen that if the equilibrium reflux boiling point is too low, that the vaporized brake fluid would easily rupture the brake hoses, resulting in failure of the brakes. Further, the brakes would not operate with vapor in the hydraulic lines.

A wet equilibrium boiling point is desired so as to test whether the inclusion of a certain amount of water in the brake fluid would result in the formation of vapor in the normal operating temperatures of the brake fluid, which would cause the rupture of the brake lines and result in failure of the brakes.

A flash point test is necessary to determine whether the brake fluid has a sufficiently high flash point. If the brake fluid does not have a sufficiently high flash point, it will start burning at the normal operating temperatures of the brakes. It is also desirable in this respect to test the fire point and the autogenous ignition temperature. For instance, if the fire point is close enough to the flash point under normal operating conditions when the flash point of the brake fluid is exceeded, the brake fluid might continue burning and would thus not only result in failure of the brakes but cause the automobile to burst into flames. In accordance with this reasoning, it is also desirable to consider the autogenous ignition temperature, for if this temperature is not considerably higher than the flash point, it can be seen that again, under operating conditions when the flash point of the fluid is exceeded and in that case ifthe autogenous ignition temperature of the fluid is also exceeded, the brake fluid might burn so quickly that not only will the brakes fail but the occupant of the automobile will not have time to leave the automobile before a major fire ensues.

A kinematic viscosity test is necessary to determine whether the brake fluid will have sufficiently low viscosity at very low temperatures and a sufficiently minimum viscosity at high tempertures so that the brakes will be in acceptable operating condition at these extreme temperatures.

A pH test is used to determine the pH of the brake fluid such that it is not acidic or too basic so that it will corrode and eat away the hydraulic lines or the hydraulic brake drum cylinders in which the fluid is located.

A high temperature stability test is necessary to determine the stability of a fluid at high temperatures so that it will not degrade at the specified temperatures to other compounds or products which would be unworkable fluids for a brake system.

A chemical stability test is needed to determine whether if the brake fluid is mixed with a glycol brand brake fluid it will not react with this fluid.

A corrosion test, as with the pH test, is needed to determine whether the brake fluid would eat away the metal in the hydraulic lines or the rubber in the brake drum cylinders or the rubber that may form part of the hydraulic lines and thus cause early failure of the brakes.

An evaporation test is needed to determine whether the brake fluid will evaporate at certain high temperatures and thus not only form undesirable vapor in the brake lines but further will result in the dissipation of the brake fluid through the hydraulic lines and master cylinder into the atmosphere so that it would need constant replacement. Excessive vapor in the hydraulic lines would cause brake failure.

A water tolerance test at low temperatures is needed to determine whether the fluid with the water it would pick up from the atmosphere would result in the water crystallizing out to form ice at low temperatures, which ice would impair the performance of the brakes.

A water tolerance test at high temperatures is needed to determine whether the water which is picked up by the fluid from the atmosphere would evaporate at the high temperature and form vapor in the brake lines which would impair the performance of the brakes.

A compatibility test is needed to determine at both low and high temperatures whether the brake fluid would operate properly when it is mixed with glycol based brake fluid and result in impairment of the performance of the brakes. This test is needed because it frequently becomes necessary to replace part of the brake fluid in an automobile with additional fluid so it is desirable for any new brake fluid which is admitted to the market to be compatible with glycol based brake fluids.

A resistance to oxidation test is necessary in order to determine whether the brake fluid will oxidize in the presence of the oxygen in the air to form different products which would be unsuitable as brake fluid components.

A stroking properties test is necessary in order that the fluid can be tested in a simulated operation that would be comparable to the use of the fluid in an automobile and thus determine the performance of the brake fluid over an extended period of time so that it may be determined that the brake fluid tested does not have any unforeseen effects which will degrade the brake hydraulic system or result in failure of the brakes.

At the present time there are no brake fluids presently in the market which pass all of the above tests with acceptable overall performance. The desirable specifications or ratings in the above suggested tests require the fluid to have a higher equilibrium reflux boiling temperature and flash point than of the presently available glycol based fluids.

The brake fluids presently on the market are basically polyether glycols which vary from case to case, depending on the type of polyether units and the number of polyether units in the polymer chain. Such brake fluids are hygroscopic in that they will pick up large quantities of water from the atmosphere. Problems are associated with the packaging and handling of such brake fluids since unless extreme precautions are exercised these brake fluids will pick-up large amounts of water from the atmosphere due to their hygroscopicity which will result in a brake fluid with poor performance characteristics as well as a brake fluid that is unsafe because it can cause a failure of the brakes. It is undesirable to have excess water since it will separate out at low temperatures such as -40F. in that the water will form ice crystals and may cause the brake drum cylinder to freeze, thus causing failure of the brakes. Further, it is undesirable to have large amounts of water in the brake fluid in that at the high temperatures, which are commonly present in the operation of automobile brakes, the water will evaporate to form vapor which may rupture the hydraulic lines causing failure of the brakes and possibly cause the brake fluid to burst into flames or the vapor may cause a very sluggish, inefflcient braking action.

It is thus desirable to have a brake fluid on the market which picks up a minimum amount of water through hygroscopicity and which is compatible with the amount of water it picks up from the atmosphere so that when the brake fluid is subjected to temperatures as low as 40F, brake failure does not result. The brake fluids which meet the above test are disclosed in the present case as well as in the applications of Frank J. Travers Docket No. 8SI-1070 Ser. No. 125,396, filed Mar. 17, 1971, Frank J. Travers Docket No. 8S1- 1071 Ser. No. 125,397, filed Mar. 17, 1971, and Frank .I. Travers Docket No. 881-1072 Ser. No. 132,556, filed Apr, 8, 1971, all filed on the same date.

Accordingly, it is one object of the present invention to provide a polysiloxane polymer useful as a brake fluid which meets the highest standards and conditions for automobile brake fluids.

It is another object of the present invention to provide an ester polysiloxane useful as hydraulic fluid for a central hydraulic system.

It is yet another object of the present invention to provide a process for producing an ester polysiloxane useful as a brake fluid.

It is an additional object of the present invention to provide a brake fluid which is only slightly hygroscopic and is compatible with the water that it picks up from the atmosphere such that the water will not separate either at low temperature or high temperatures from the brake fluid mass.

It is yet another aim of the present invention to provide a polysiloxane polymer useful as a brake fluid which has a high flash point, fire point and autogenous condition temperature which far exceeds those of the brake fluids presently on the market.

SUMMARY OF THE INVENTION In accordance with the present invention there is provided a brake fluid system comprising brake drum cyl inders, a master cylinder, hydraulic lines connecting the brake drum cylinders to the master cylinder where said hydraulic lines and brake drum cylinders, as well as the master cylinders, containing a polysiloxane polymer of the structure,

where R is a monovalent hydrocarbon radical or a halogenated monovalent hydrocarbon radical, R' is a divalent hydrocarbon radical, E is selected from the group consisting of R, R-OR',

R(OC,,H R-Ol-1, and R(OH) where R is a polyvalent hydrocarbon radical having 5 number hydroxyl groups, where s varies from 2 to 5, n is a whole number that varies from 2 to 4 and z varies from 1 to 4 where a varies from 1.1 to 202, b varies from 0.023 to 1.00, and the sum of a b varies from 2.024 to 3.00. More specifically, R is selected from alkylene or arylene radicals of up to 20 carbon atoms and R is preferably an alkyl radical such as methyl. Further, more preferably, a varies from 1.23 to 2.05, b varies from 0.055 to 0.92 and the sum of a b varies from 2.074 to 2.5. This polysiloxane polymer is obtained by reacting an alkenoic acid with an alcohol in the presence of an acid catalyst so as to esterify the alkenoic acid and then reacting the resulting ester by SiH-olefin addition with a hydropolysiloxane in the presence of a platinum catalyst.

DESCRIPTION OF THE PREFERRED EMBODIMENT The radicals R and R appearing in formula (1) are well known in the art and are typified by radicals usually associated with silicon-bonded organic groups in the case of R and are generally associated with divalent hydrocarbon radicals in the case of R.

The organic radicals represented by R include mono valent hydrocarbon radicals, halogenated monovalent hydrocarbon radicals and cyanoalkyl radicals. Thus, the radical R may be alkyl, such as methyl, ethyl, propyl, butyl, octyl; aryl radicals such as phenyl, tolyl, xylyl, napthyl radicals; aralkyl radicals such as benzyl, phenylethyl radicals; olefinically unsaturated monovalent hydrocarbon radicals such as vinyl, allyl, cyclohexyl radicals; cycloalkyl radicals such as cyclohexyl, cycloheptyl, dichloropropyl, 1,1,1-trifluoropropyl, ehlorophenyl, dibromophenyl and other such radicals; cyanoalkyl radicals such as cyanoethyl, cyanopropyl, etc. Preferably, the radicals represented by R have less than 8 carbon atoms and in particular it is preferred that R be methyl, ethyl or phenyl. The radicals represented by R may be any alkylene or arylene radicals of less than 20 carbon atoms such as methylene, ethylene, various isomers of the phenylene radicals or substituted phenylene radicals. In the preferred embodiment R is propylene. Further, R can be alkylene, arylene, alkenylene, as well as alkynylene.

The preferred structural formula which comes within the average unit formula as set forth in formula (1) is as follows:

lri this formula, R is preferably methyl, it varies from 1 to 10 and y varies from l to l5. It should be noted that in this formula and in the average unit formula R is attached to the carbonyl bond and R, as a constituent of the radical E, may he the same or different. Usually the divalent radicals are different.

The compound of formula (1) may also have the structural formula as follows:

One method for forming the compounds of formula (I comprises the reaction of a compound of the formula CH (HR-Cl with cuprous cyanide to form CH CHR CN. where R is a divalent hydrocarbon radical ofup to carbon atoms. The reaction is preferably carried out at room temperature in the presence of an inert $Ul\ ent such as benzene, toluene, xylene and (llli mineral spirits. The cyanide product is then taken and reacted with hydrochloric acid and water at a temperature in the range of to lO0C to form the compound CH CHR COOH.

Another method for forming the olefiriic acid or the alkenoic acid is to take the alkenyl chloride CH CHR CI and react that with NitCO) under a pressure of 50 psi in the presence of carbon monoxide and at a temperature in the range of 50 to 150C so as to form the resulting compound which is CH CHR -COCI. This carbonyl chloride may then be reacted with water to form the alkenoic acid product. The alkenoic acid may then be reacted with the required alcohol to form the desired ester. Thus, the alkcnoic acid CH =CHR COOH may be reacted with alcohols of the formula ROR'OH, R(OC,,H ,,O),OH. HOR'-OH and HOR" (OH), to form the desired ester. The esterifr cation reaction is preferably carried out in the presence of the catalyst which may be a strong acid such as sulfuric acid. hydrochloric acid or nitric acid. Preferably, the catalyst is sulfuric acid or toluene sulfonic acid. Although the reaction may be carried out at room temperaturc, it has been discovered that the esterification reaction proceeds too slowly at that temperature. Prefcrahly the reaction temperature is in the range of 50 to I50C and more preferably in the range of to |30C The reaction is allowed to proceed for 2 to l5 hours and preferably from 5 to l0 hours. Further, the esterification reaction is preferably carried out in the presence of an inert solvent selected from toluene and xylene, benzene, mineral spirits and other inert solvents. After the reaction has proceeded to completion, that is after the reaction period of 5 to [0 hours, the acid is neutralized with sodium bicarbonate and additional inert solvent is added to the reaction mixture. Then the organic layer is washed with water and the resulting organic layer is separated from the aqueous layer that forms. Then the ester is distilled from the organic layer by distillation procedure so as to separate out the pure ester material. When diols or polyols are used in the esterification procedure. it is preferable that at least 10 and preferably at least 20 percent by weight excess of the alcohols be used in addition to the stoil CH:

chiometric amount necessary to react with the alkenoic acid such that it will prevent the formation of diesters in the esterification procedure. in place of the esteril'ication reaction, the alkenoic acid maybe reacted with sulfonic chloride so as to give an alkenylcarbonyl chloride product. This reaction is preferably carried out at room temperature, that is 20 to SOT l'he reacted acid chloride can then be reacted with any alcohol in the presence of a basic media such as ammonia, triethylam ine. pyridine, as hydrogen chloride acceptors at room temperature, to produce the resulting acid compound.

To produce the desired reaction products of the present case. the ester is then reacted with a compound of the formula R H u a fill? in the presence of a platinum catalyst, where R has the meaning defined previously and a varies from l.ll to 202.11 varies from 0.023 to I and the sum ofa h varies from 2.024 to 3.00. Preferably in the above formula. a varies from L23 to 2.05. h varies from 0.055 to 0.92 and the sum of a plus I; varies from 2.074 to 2.5. The hydropolysiloxane is added to the reaction pot and heated to a temperature in the range of l00 to 150C to remove any free water and toluene is then added to the reaction pot. The mixture is heated to a temperature in the range of lO0 to l50C to remove any free water by toluene-water azeotrope. Once the solution of the hydropolysiloxane and the toluene is dried in accordance with the azeotrope technique a trace of platinum catalyst is added to the mixture. Then the alkenoie acid ester is slowly added to the reaction pot. The addi tion is csotherrnic so the temperature is controlled by the olefin addition rate and is usually maintained in the range of 15 75C. During the reaction. the SiH peak disappearance is t'olloned by infrared scan. Once the addition of olel'in to silicon hydride is completed. the solution i filtered through Fuller's Earth to remove any precipitates Then the solution is stripped to remove solvents and low boiling fractions to yield the desired polysiloxane which falls within formula (l) and'which is the desirable brake fluid of the present case. By the rate of the addition of the olefin. the temperature is able to be controlled in the range of 25 to l00C and. more prctcriihly, iii the range of 25 to 75%.

uit.il lc catalyst for addition of orgaiioliydrogciil \.\llt \illlL to the alkcnoic acid e ter arc the various platinum and platinum compound catalysts l\llt\WiI iii the art lhcsc catalysts include clcnicutal platinum iii the finely dii ided state which can be deposited on char coal or alumina. as well as various platinum compounds such as chloroplatinic acid. the platinum hydrocarbon complex of the type shown in US. Pat. Nos. 3.l59,60l. 3.159.662. as well as the platinum alcoholic complexes prepared from chloroplatinic acid which are described and claimed in Lamoreaux US. Pat. No. 3220972. Preferably. the platinum catalyst is added to the organohydrogenpolysiloxane located in the reaction chamber to which is also added a solvent and then al kenoic acid ester is slowly added to the reaction mixture at the reaction temperatures described above. Whether elemental platinum or one of the platinum complex catalysts is used, the catalyst is generally used in amounts sufficient to provide about 10" to l0 moles of platinum per mole of the alkenoic acid ester reactant. As mentioned previously. the reaction is effected by adding the organohydrogcnpolysiloxane to an inert solvent such as inert solvents being selected from the group of benzene. toluene. xylene mineral spirits and other inert solvents The reaction mixture is prefer ably heated to 25 to 75 C before the addition of the zilkenoic acid ester. The alkenoic acid ester is then added to the hydrogcnpolysilo tane solvent mixture at an addition rate so as to maintain the reaction temperature in the range of to 75C during the reaction err Preferably, the reaction is allowed to proceed to completion in 4 to l5 hours and preferably in 5 to 8 hours. After the reaction period is over, a sample of the reaction mixture may be checked by infrared analysis for SiH bonds to determine how far the reaction has pro ceeded to completion. When at least percent of the SiH orgariopolysiloxane has been converted to the reaction product, the reaction mixture may be cooled and the reaction may be considered to have proceeded to a sufficient extent for the conversion of the ester polysiloxanc.

In the case where the ester with the alkenoic acid ester has free hydroxyl groups the SiH-olefin addition reaction may be carried out in the presence ofa buffer in order for the reaction to properly proceed. Any of the commonly known buffers may be used to buffer the reaction mixture or solution containing the hydrogenpolysiloxane and the solvent therein such that the reaction procceds in accordance with the desired condi' tions.

Another method of protecting the free hydroxyl groups in an alkenoic acid ester having such free hydroxyl groups is to first react the alkenoic acid ester with trirnethylchlorosilanc such that the trimethylchlo rosilane attaches itself to the free hydroxyl groups. The SiH-olcfin addition reaction can then be carried out without any buffer present A fter the reaction product has been obtained from the reaction. then the polysiloxanc cstcr can be suhyccted to a mild hydrolysis with water or a trace amount of a weak acid can he added to the polysiloxane ester so as to liberate the trimethylsilanc group and form hydroxyl units at the terminal position of the polysiloxane ester such that it once again has free hydroxyl groups. This method i8 only used when the ester moiety has free hydroxyl groups attached to it so as to allow the SiH-olefin addition reaction to proceed in the proper manner.

Preparation of the organohydrogenpolysiloxane of formula (4] which can contain both saturated and olelinically unsaturated hydrocarbon groups may be carried out by any of the procedures well known to those skilled in the art Such polysiloxaucs can he produced by following the procedure involving the hydrolysis of one or more hydrocarhon-suhstitutcd chlorosilanes in which the substituents consist of saturated hydrocarbon groups the crude hydrolyzate containing a mixture of linear and cyclic polysiloxanes. Further, one or more hydrocarbon-substituted chlorosilanes with hydrocarbon-substituents comprising one or more olefinically unsaturated hydrocarbon groups are hydrolyzed to produce a crude hydrolyzate containing a mixture oflinear and cyclic polysiloxanes. The two crude hydrolyzates are polymerized by being treated with KOH to form mixtures of low boiling, low molecular weight cyclic polymers mixed with undesirable materials such as monofunctional and trifunctional chlorosilane starting material. The resulting compositions are fractionally distilled and there is collected two pure products of the low boiling low molecular weight cyclic polymers free of any significant amount of monofunctional and trifunctional groups. ln order to dcpolymerize the two by drolyzates there is added to them a catalyst and the mixture is heated to a temperature above I50C to produce and recover by evaporation a product consisting of low molecular weight cyclic polysiloxanes comprising, for example about 83 percent of the tetrasiloxane and l5 percent of the nii ted lftStllitliflC and pentasiloio anc The distillate consisting essentially of low molecular weight cyclic dimethyl polymers free of any significant amounts of monofunctional and trifunctional groups is collected in the vessel. The then dried cyclic siloxane contains less than parts per million of water The cyclic methylvinyl and diphenyl cyclic siloxanes are prepared in the same way. The two cyclic siloxanes are added in the desired proportions in a reaction vessel so as to be subjected to an equilibrium reaction to form the hydrogenpolysiloxanes of formula [4). Thus, about 2.5 to 17 mole percent cyclic diphenylsiloxane can be added to R3 to 97.5 mole percent dimethyl cy clic siloxanes. lf desired. and depending upon the type of compound that is to be produced. 0.] to l.(l mole percent of inetliylvinyl cyclic siloxane may be mixed with diinethyl and diphenyl cyclic siloxanes or other desired proportions of the cyclic siloxanes can be used to produce the desired polymer. To the above mixture ol purc cyclic siloxanes there is added a polymerization catalyst such as KOH. The potassium hydroxide breaks a ring of cyclic siloxane to form a potassium silonate, which can then attack other cyclics to break the rings and increase the chain length of the siloxanes formed. There is further added to the reaction mixture in the amount of one or more monofunctional compounds calculated to function as end-blockers for limiting the degree of polymerization and consequently the lengths and molecular weights of the linear polysiloxane chains, and for tabilizing the polymers.

L'sually a small amount of monofunctional compounds are added to function as cndblockers so as to regulate the chain length of the polymers. The func tional compounds there maybe employed satisfactorily for controlling polymer growth include, among others. bexamethyldisiloxane. tctramethyldiethoxydisiloxane, diethyltetraethoxydisiloxane. divinyltctraethoxydisiloxaiie. and decawnethyltctrasiloxane. The equilibration reaction I\ carried out from I to 4 hours until about 85 percent of the cyclic diorganosiloxzines have been con- \crlcd to polynici end stopped with monol'unctional groups, When the 85 percent conversion point has been reached. there .irc'just as many polymers being converted to cyclic siloxancs as there are cyclic silox tines being converted to the polymers At that time there is added to the mixture a SlllllClClll amount of an .tClLl donor such as phosphoric acid. that will neutralize the KOH catalyst so as to terminate the polymerization reactionv The cyclic diorganosiloxanes in the reaction mixture are then distilled off to leave the polyhydrogensiloxane which is useful in the present invention. Hydrocarbon-substituted polysiloxanes with pending groups consist largely of groups other than methyl, such as ethyl or the saturated hydrocarbon groups and olefinically unsaturated hydrocarbon groups other than, or in addition to, vinyl groups can be produced by means of procedures similar to those described above or by the means of procedures modified in accordance with the characteristics of the hydrocarbon groups to be included.

The above procedure can be used to produce branchchain polysiloxanes. as well as linear diorganopolysiloxtines. depending on the reactants that are used in the equilibration reaction.

To produce the hydrogcnpolyorganosiloxane of the present case which is used in the SiH-olefin addition reaction and which are represented by the average unit formula (4). hexaniethyldisiloxane is equilibrated with octaniethyltetrrisiloxane and tetramethyltetrahydrogentetrasiloxane in the proper molar proportion. in the presence of 3 percent of acid-treated clay. such as .1 percent acid on Fuller's Earth and the reaction mixture is heated for 5 hours at lUO to lEO C to equili' brate the reaction mixture. After 5 hours of reaction time, when approximately percent of the tetramers have been converted to the polymer polysiloxane, the catalyst is neutralized with a weak base and the volatile cyclics are distilled off to leave a substantially pure polyorganosiloxane. By using dihydrogentetramethyldisiloxane as the chain-stopping unit instead of hexamethyldisiloxane, there can be obtained a linear polysiloxane having hydrogen groups at the terminal positions of the polymer chain, as well as in the center position of the polymer chain. Such a polymer product allows the production of alkenoic acid ester polysilox- .incs with the alkenoic acid groups attached by SiH- oleliri addition reaction at the terminal positions of the chain. :is well as in the center position of the polymer chain.

Besides the number of other advantages. such as a higher flash point, fire point and auto ignition temperature. as well as much lower water pick-up than the brake fluids presently on the market, the brake fluids of the present case have the advantage that they are paintable. that is. if they are spilled on a portion of the automobile, the fluid will not stain or remove the paint on the surface with which it comes in contact. This is not the case with standard brake fluids which, upon coming into contact with the painted area in an automobile, will either take the paint off or stain it so that the painted area has to be repainted. This advantage is especially pertinent for automobile manufacturers where a large amount of brake fluids are handled and in which cases the brake fluids are quite often spilled on the painted areas of the automobiles. In those cases, the automobiles have to be repainted. However, since the fluids ofthe present case do not affect the paint, the brake fluid of the present case can be merely wiped off the painted area without any effect whatsoever on the painted area below.

Another advantage of the brake fluids of the present case is that they are non-toxic, that is, they do not give off toxic fumes and do not affect the skin or cause dermatitis of any type or sort. With the brake fluids presently on the market and especially in the case where mechanics and factory workers have to handle large amounts of brake fluids. it is very often the case that the workers develop some sort of a dermatitis as a re sult of contact with the brake fluids. It is understood, ofcourse. that the polysiloxanes of the present case can be used as hydraulic fluids in any type of hydraulic system as well as a brake hydraulic system.

A dry equilibrium reflux boiling point test is carried out by placing 60 mm of brake fluid in a flask and boil ing under specified equilibrium conditions in a lOO ml flask. The average temperature of the boiling fluid at the end of the reflux period is determined and corrected for variations of barometric pressure if neces sary, as the equilibrium reflux boiling point. The brake fluids of the present case have an equilibrium reflux boiling point of 500F or above.

The next test is the wet equilibration reflux boiling point which is carried out by taking a ml sample of the brake fluid which is humidified under controlled conditions, then 100 ml of SAE compatibility fluid is used to establish the end point of the humidification. After humidification, the water content and the equilibrium reflux boiling point ofthe brake fluid are determined as in the previous test. When our fluid is run under the test conditions set forth above, there is obtained an equilibrium reflux boiling point of 324 to 340" or greater. depending upon the rate at which the brake fluid is heated.

For the flash determination. the test is to take a test dish which is filled to a specified level with brake fluid. The fluid temperature is increased rapidly and then at a slower rate as the flash point is approached. At specified intervals. a small test flame is passed across the cup. The lowest temperature at which application ol the test flame causes vapors above the fluid surface to ignite is the flash point. The brake fluids of the present invention have a flash point ol' 25(ll" and greater.

ll' some of the volatiles are stripped ofl from the brake fluid ol' the present case, the flash point can be increased to exceedingly higher temperatures.

The procedure to determine the flre point is the same as that for determining the flash point. The fluid is heated and vapor is ignited and the flames passed over the vapor ol the fluid until the vapor is ignited and the fluid continues to burn.

To determine the autogenous ignition temperature. one I25 ml flask is immersed into a molten lead bath.

The temperature of the molten lead bath is continually I tion temperature. With the fluids of the present case the flrc point is greatert than llttT and the autogcnous ignition temperature is 750F or greater As mentioned previously. the fire point and the autogenous ignition temperatures should be considered in order to deter mine the probability of the brake fluid causing a Fire With the fluids ol' the present tHVCfllltlll. because ol' their higher flash points and autogenous ignition lLltt peratures. it is very unlikely that the brake fluid trill burn or cause a tire in an automobile because l:lL'ill\ or a rupture in the brake fluid line The brake fluids of the present case have also been subjected to a standard fire test where 40 g. of the brake fluid are placed in a tilt nil beaker and the beaker then placed in a rotating stage oven which is inanitained at 500F. With the glycol based fluids. after they have been inserted into the rotating oven for l minutes. they burst into flames and continue to burn. Even after the flames have been extinguished and the fluid has again been exposed to oxygen. the glycol based fluids will immediately ignite and continue to burn. With the fluids of the present case which were subjected to the same test. the fluids survived l2 hours with some vapor loss in the rotating stage oven which was maid tained at 500F, thus showing that the fluids ofthe present case were considerably more stable and non combustible at high temperatures.

The kinematic viscosity test is a determination of the measure olthe time necessary for a fixed volume of the brake fluid to flow through a calibrated glass capillary viscosimeter under an accurately reproducible head and a closely controlled temperature. The kinematic viscosity is their calculated trorn the measure oi flow time and the calibration constant of the viscosinieter At 4llC the brake fluids of this invention have a vi cosity Ur 7(ltl to lhtlll eeiilistoitc At 1| I l" the brake fluids ol the present case have a viscosity that exceeds that of the glycol based fluids In the pH value determination a quantity ol the brake fluid is diluted with an equal volume ot a me thanol-water solution, The pH of the resulting mixture is measured with a prescribed pll meter assembly at 23C For all types of brake fluids, the brake lltlltls ;is tested must have a pH of not less than 7 or more than l ll). A mild base is added to the brake fluids of the present invention such that as measured by the above pH method. the pH of the fluid is 7.2 to 9.6. A mild base that can be added to the fluids of the present case so that they will pass the pH standard test is barium hy droxide.

The brake fluid stability test comprises a high tern perature stability test and a chemical stability test. In the case of the high temperature stability test. a mm sample of the brake fluid is heated to an appropriate holding temperature, and then the brake fluid is maintained at the holding temperature for I20 i 5 minutes. Then, for the next 5 t 2 minutes. the fluidis heated to an equilibrium reflux rate of l to 2 drops per second and the temperature is taken. The fluids of the present case pass this test.

ln the case of chemical stability, 30 1': l ml of the brake fluid is mixed with 30 :1 ml of SAE l compati bility fluid in a boiling flask. First the initial equilibrium reflux boiling point of the mixture is determined by applying heat to the flask so that the fluid is refluxing at It) i 2 minutes at a rate in excess of l drop per second Then over the next l5 t 1 minute, the reflux rate is adjusted and maintained at l to 2 drops per second. This rate maintained for an additional 2 minutes and the average value is recorded as the final equilibrium reflux boiling point. The brake fluids of the present case also pass this test.

The corrosion test comprises polishing, cleaning and weighing 6 specified metal corrosion test strips and assembling them as prescribed in the standards. This assembly is placed on a standard rubber wheel cylinder cup in a corrosion test-jar and immersed in the brake fluid. capped and placed in an oven at lOOC for I20 4 hours. Upon removal and cooling, the strips and the fluid cup are examined and tested. The metal test strips are observed to note whether pitting or etching are discernible. whether there are any crystalline deposits which form and adhere to the glass jar walls or the sur face of the metal strips, and whether there is sedimentation in the fluid-water mixture. The metal strips are weighed for weight loss and other determinations are made with respect to the test. The brake fluids of the present case pass this test without any difficulty.

Another test was carried out by the present inventor in order to determine the chemical stability of the fluids of the present case as compared to the glycol based fluids that are available on the makret. In the test. 40 g. of each fluid was taken and placed in a 150 mm beaker and placed in a rotating stage oven which was maintained at 400F. The high temperature glycol based fluids were 80 percent volatilized in 5 hours. The ultra high temperature glycol based fluids were 30 percent volatilized in 5 hours and the fluids of the present case were volatilized only 5 percent in the same number of hours. In a 20 hour period, the high temperature glycol based fluid was 83 to 84 percent volatilized. The ultra high temperature glycol based fluid, in 20 hours. was percent volatilized and the fluids of the present case were only 13 percent volatiliaed. indicating the thermal and chemical stability of the fluids of the present case as compared to the brake fluids presently on the market.

The fluidity and appearance low temperature test comprises taking brake fluid and lowering it to expected minimum exposure temperatures such as 40C and the fluid is then observed for clarity, gelation, sedimentahon. excessive viscosity or thixotropicityv The brake fluid of the present invention with the amount of water that it absorbs from the atmosphere or through osmosis in the hydraulic lines of a brake fluid system absorbs less than 0.5 percent by weight water and usually less than 0.3 percent by weight of water. The brake fluid of the present case has no crystallization. cloudiness, stratification or sedimentation and upon reversion olthe sample bottle in which the test is carried out. the time required for the air bubble to travel to the top of the fluid is less than seconds. Our fluid passes this test without any difficulty.

ln the evaporation test, ml of brake fluid is placed in a covered dish for 48 hours at IOOC in an oven. It is then taken out and then returned to the oven for 24 hours at l00C and this is continued for a total period of 7 days. The nonvolatile portion is measured and examined for residues. The residues are then combined and checked for fluidity at 5C. in the present case there is only a loss of 3 percent by weight of volatiles after the 7 day period.

In the water tolerance test, the brake fluid is diluted with water and stored at low temperatures of -C to *5()C for 14 hours. The cold water wet fluid is first cxamined for clarity. stratification and sedimentation and placed in an oven at 6QC for 24 hours. On the removal it is again examined for stratiflcation and the volume per cent of sedimentation by centrifuging. The brake fluid ofthe present case is SUbJCClCCl to this test with the amount of water that normally it would pick up from the atmosphere upon being exposed to the atmosphere for an extended period of time. or the amount of water it would pick up for an extended period. such as several months or a year or more through osmosis throu' h the hydraulic brake lines, assuming that the hycliaulic brake lines were immersed in water. This amount of water is less than 0.3 percent by weight of the hydraulic brake fluid As a result, the ester polysiloxane brake fluid of the present case passes this test.

ln the compatibility test, a sample of the brake fluid is mixed with an equal volume of SAE 1 compatibility fluid then tested in the same way as for water tolerance except that the bubble flow time is not measured. The test is an indication of the compatibility of the test fluid with other motor vehicle brake fluids at both high and low temperatures. The polysiloxane brake fluid of the present invention passed this test without any difficulty.

In the resistance to oxidation tests, the brake fluid is activated with approximately 0.2 percent benzoyl per oxide and 5 percent water. A corrosion test strip assembly consisting of a cast iron and aluminum strips separated by tin foil squares at each end are then rested in a piece of SBRWC cup so that the test strips are half immersed in the fluid and oven aged at 70C for I66 hours. At the end of this period the metal strips are examined for pitting. etching and weight loss. The polysiloxane brake fluid of the present case, when it was sub jected to this oxidation test, passed the test without any difficulty and there was no residue or deposits formed as the result of oxidation The next test is the effect on rubber where the four selected SASBRWC rubber cups are measured and their hardness determined The cups, two to a jar, are immersed in the test brake fluid. one jar is heated for l2(l hours at 70C and the other for 70 hours at l2llC After the cups are washed and examined for disintegrze tion, they aic renieasured and their hardness redetermined The polysiloxane brake fluid of the present case passed this test without any difficulty,

The final test is the stroking properties test. In this test, the brake fluid is stroked under controlled condi tions at an elevated temperature in a simulated motor vehicle hydraulic brake system Consisting of 4 slave wheel cylinders and a master cylinder connected by steel tubing. Standard parts are used. All parts are care fully cleaned, examined and certain measurements made immediately prior to assembly for test. During the test, temperature, rate of pressure rise. maximum pressure and rate of stroke are used as specified. The system is examined periodically during stroking to as sure that excessive leakage of fluid is not occurring. Afterwards, the system is torn down, metal parts and rub ber cups are examined and remeasured. The brake fluid and any resultant sludge and debris are collected. examined and tested. The polysiloxane brake fluid of the present case also passed this test without any difficulty.

The polysiloxarie brake fluid of the present case was also tested in accordance with a Federal test on corrosive instability of light oils. The polysiloxane ol the present case was put into a tube and then metal plates on a hanger were placed in a tube such that they were covered with the fluid. A condenser was then placed above the tube and the tube was heated to ltltlF so that reflux could take place and the tube was heated to 200F for I68 hours. Then the metal sample plates were taken out, wiped and checked for corrosion and the fluid was checked for deposits or residue or stratit'i cation. The polysiloxane brake fluid otthe present case also passed this test without any difficulty As mentioned previously, the polysiloxane brake fluids of the present case far exceed the specifications of the high temperature glycol based fluids and the ultra high glycol based fluids in terms of flash points, in the evaporation test, thermal stability. chemical stability and in other tests. Not only is the polysiloxane brake fluid of the present invention more stable at high temperatures, it has a much lower viscosity than that speei tied for the best low temperature glycol based fluid presently on the market.

Brake fluids may be prepared according to the pres ent invention which has a viscosity of as low as 600 centistokes at 40C. The advantage of this is that there is no sluggishness in the brakes at low temperatures. ln fact. the brake fluid of the present invention meets the specifications for arctic brake fluids.

Another advantage of the brake fluid of the present case is its low water hygroscopicity or pick-up from the atmosphere. in fact, the polysiloxane brake fluid of the present invention can be said to repel water rather than to attract it and add it to the polysiloxane mass. ln fact, no more than 0.22 weight per cent of water is picked up by the polysiloxane brake fluid of the present case when the brake fluid is immersed in a standard brake hydraulic rubber hose which is immersed in a water bath over an extended period of time. The brake fluid of the present invention will pick up even less water from the atmosphere upon being exposed to a humid atmosphere for periods as long as one year or more With this amount of water moisture, in fact with up to 0.5 weight per cent of the polysiloxane as water mixed in with the polysiloxane brake fluid. there is no failure of the brake at extremely low temperatures such as 4()C and there is no failure of the brake at high ternperatures such as lO0C.

Brake fluids presently on the market, that is glycol based brake fluids. are notoriously hygroscopic; such brake fluids will pick up from the air large amounts of water, which moisture may cause failure of the brakes at low temperatures or which may cause failure of the brakes at high temperatures to cause sluggish action of the brakes or rupture of the hydraulic brake lines.

The following examples are given below in order to better illustrate the present invention without intending to limit the invention. In the examples below, the symbol Y stands for high temperature glycol based fluids and the symbol ZY for ultra high temperature glycol based fluids All parts are by weight.

EXAMPLE I into a l lttLIl' l-neck flask equipped with a Yliead, thermometer. addition funnel, condenser and a heating mantle there was added l50 parts ol (CH;,) SiO[(CH; HSi()l ,llCH SiOl,,+ SUCH and 200 cc toluene. The solution was heated to 120C to remove any free water as a toluene-water a/cotrope. Once the solution was dried by way of the azeotropc, 005 per cent Lamoreaux catalyst was added to the solution. At this time, there was then added (ill parts of CH =CHCH OOCH to the reaction pot The addition is exothermic so the temperature of reaction is. controlled by the olefin addition rate The -Qill peak disappearance was followed by infrared scans Once the addition of the olefin-silicon hydride was completed in accordance with the infrared scan. the solution was filtered with Fullers Earthand Celite 545. Then the solution was stripped to remove the soltents and low boiling fractions yielding a low viscosit silicone polyester brake fluid. The yield of stripped fluid was about 80 percent. The yield product, which had the lorniula.

(Elli had the following properties:

fem pcrature Viscosity in Centislokes 27F l7 llJtlF l3 ZTZ F 5 Open cup flash point 440T Water solubility O 3 v 0.5%

EXAMPLE 2 lnto a liter, l-neck round bottom flask equipped with a mechanical stirrer. Yhead. thermometer, addition l'nnnel. condenser and heating mantle, there was added lll pails iil ((llJ SiUI ((ll HlSiOM(CHfl Si- ()|,,,\|(('ll .tlltl illtl cc of toluene The solution was heated to l3l)"(f to remove any free water by toluenewater aaeotropc Once the solution was dried via the azeotrope technique, 0.07 per cent of Lamoreaux platinuni catalyst was added to the mixture. Then 95 parts of (ill: LHCll COOC H CH OCH was slowly added to the reaction pot The addition is exothermic so the reaction is controlled by the olefin addition rate and is maintained at 50 to 60C. The SiH peak disappearance was followed by infrared scan. Once the addition of olefin to silicon hydride was complete according to the infrared scan, the solution was filtered with Fuller's Earth and Celite 545. Thereafter, the solution was stripped to remove solvents and low boiling fractions yielding a low viscosity silicone brake fluid. The yield of stripped fluid was about 80% of the reaction and the final structure of the product was H tullmc n ((ilhhttfilli This fluid had a viscosity of 2,400 centistokes at b7"F whereas the fluid of Example I had a viscosity at 67"F of 600 centistokes.

EXAMPLE 3 Into a l liter, 3 neck round bottom flask equipped with a mechanical stirrer, Y-head, thermometer. addi' tion funnel, condenser and a heating mantle there was added 150 parts of (CHHJSXOHCHJ)slollllcl[JIESlUlgStlCllyli I l and 250 cc of toluene. The solution was heated to l 35C pot temperature to remove any free water by toluene-water azeotrope. Once the solution was dried by way of the azeotrope, 0.08 per cent Larnoreaux platinum catalyst was added to the mixture Then 85 parts of was slowly added to the reaction pot. The teiitperaturc is controlled by the olefin addition rate such that it is maintained between 50 to 70C The SiH peak disap pearance was followed by infrared scanv Once the addition of the olefin to silicon hydride was complete according to infrared scan. the solution was filtered through Fuller's Earth and Celite 545. Then the solution was stripped to remove solvents and low boiling fractions yielding a low viscosity silicone brake fluid The yield of the stripped fluid was about and had the following structure:

Into a 1 liter, 3-neck round bottom flask equipped with a mechanical stirrer, Yhead, thermometer, addition funnel, condenser and a heating mantle there was added I50 parts of H(CH ),SiO[H(CH;)SiO} [(CH SiO] Si(CH ),H and 200 cc of xylenev The solution was heated to I40C pot temperature to remove any free water by toluene-water azcotropc. Once the solution was dried via the azeotrope, 005 per cent Lamoreaux platinum catalyst was added to the mixture Then 144 parts of CH: CH-Cl l,(0()CH,CH OCH was slowly added to the reaction pot. The addition is exothermic so the temperature is Controlled by the olefin addition reaction rate. The SiH peak disappearance is followed by infrared scan. Once the addition of olefin to silicon hydride is completed, according to the infrared scan. the solution is filtered through Fullers Earth and Celite 545 Then the solution is stripped to remove solvents and low boiling fractions yielding a low viscosity silicone ester brake fluid. The yield of stripped fluid is about 90% and has the following structure:

(J J [I ll oi i'li i oi It 1- li'iiti-silltt'ltisioiilt llui tliihittillm EXAMPLE lnto a t liter, 3-neck round bottom flask equipped with a mechanical stirrer. Yhead, thermometer. addition funnel. condenser and heating mantle, there was added l 50 parts of (CH; SiOl(CH )HSiO] [(CH Si- OI SHCHQ and 300 cc of toluene. The solution was heated to 140C pot temperature to remove any free water by toluenowater azeotrope. Once the solution was dried by way of the azeotrope technique. 0. l0 per cent Lamoreaux platinum catalyst was added to the mixture. Then 240 parts of CH CHCH COO(C H O) CH CH CH was slowly added to the reaction pot The addition is e irothermic and the rate of addition is controlled so that the temperature is regulated at 70 to 80C The SiH peak disappearance is followed by an infrared scan Once the addition of olefin to silicon hydride is completed according to infrared scan. the solution is filtered through Fuller's Earth and Celite 545. Then the .\()lUllUlt is stripped to remove solvents and low boiling fractions yielding a low viscosity silicone ester brake fluid. The yield ofester brake fluid about 85 percent and has the following structure: I

and 250 cc toluene. The solution is heated to I20C pot temperature to remove any free water by toluene-water azeotrope. Once the solution is dried via the azeotrope technique, about 0.07 percent Lamoreaux platinum catalyst is added to the mixture. Then I parts of CH =CHCH COOCH CH CH OH is slowly added to the reaction pot. Before the addition of this compound. there is added to the hydrogenpolysiloxane 100 cc of a potassium hydrogen phthalate buffer solutionv In place of this buffer solution there may also be used a barium sulfate buffer solution. The addition of the compound to the hydrogenpolysiloxane is exothermic so the temperature is controlled: by the olefin addition rate. The SiH peak disappearance is followed by an in frared scan. Once the addition of olefin to silicon hydride is completed according to the infrared scan, the solution is filtered in Fuller's Earth and Celite 545. Then the solution is stripped to remove the solvent and low boiling fractions yielding a low viscosity silicone ester brake fluid. The yield of stripped fluid is about 85 percent and has the following structure:

EXAMPLE 7 The ester polysiloxane of Example 2 is placed in a heated chamber which is maintained at 80 percent relative humidity and allowed to pick up moisture for a three day period. A standard Y fluid and 2Y fluid are also treated in the same manner. The viseosities of these Y and ZY fluids were compared to the Example 2 fluid with the amount of water that was picked up in the three day period, as well as the amount of water in it uniwoii HMwl-lo l t the fluid during its initial state is recorded in Table l for i'lll t\('l ()((';ll;()) l'llyl'llgl'll; different temperatures TABLE I VlSCOSlTY TEMPERATURE F 77F IOU"F ZIUF ZY Fluid (2.78% HOH) 2730 cs l6 cs l0 5 cs 2 9 cs ZY Fluid (0.072% HOH) I635 cs l5 cs 9.5 cs 2.6 cs Y Fluid (310% HOH) 746 cs ll 8 cs 8 cs 2.5 cs Y Fluid (Dry) N.A. l0.l cs 7 2 cs 2.4 cs Y Fluid (0.90% HOH) 888 cs I5 cs l0 6 cs 3.l cs Example 2 (0.l769l HOH) i230 cs 32 cs 23 cs 7.} cs

Fluid Example 2 (0% HOH) llOO cs 32 cs 2] cs 7 cs Fluid 1 days at RH at 77'F EXAMPLE 6 55 From the results of the table, it can be seen that the lnto a l liter, 3'neck round bottom flask equipped with a mechanical stirrer, Y-head, thermometer, addition funnel. condenser and heating mantle there was added 250 parts of Example 2 fluid is comparable in viscosity characteristies to the Y and ZY fluids.

The fluid of Example 2 is then taken and stripped at different temperatures and pressures and the viscosity characteristics are then recorded with respect to the different samples at the different temperatures in Table ll below. The flash point and fire points ofthe fluids are also recorded.

TABLE ll Viscosities at Various Temperatures Stripping 7 Flash Fire Sample \11 Conditiom 4l)F 77F lOOF 2l0F Point Point trample Z l til I71! iii 5 mm 667 c\ 2] fi cs If) 9 cs 55 cs TSUF 420T l X l :tPlL2 Ztltl'T al 2 mm HIKE cs 32 l cs 22 H cs 7 cs 45IIF 49HF l l il l'l lplt' Z 2701' al 2 mm I676 L\ 46 cs 12,! c Ill 9 cs 53llF (iflll h lluid lt was felt that it was necessary to subject the fluid of the present case to a more severe test as to the amount of water it could pick upv ln order to do this, the standard Y fluid was taken and placed in a rubber Bendix hydraulic part No. 8237. which is a rubber hose commonly used as a hydraulic brake line. The rubber hose filled with the Y standard brake fluid was then capped at both ends bent to a U-shape and immersed in water to the metal fitting and allowed to stand in the water bath for 9 days. The same procedure was repeated with a sample of Example 2 fluidv After the 9 day period. the fluid was removed from the rubber hose and its water content determined. The water content of both the standard Y fluid and the Example 2 fluid before immersiori in the water bath and after the removal from the water bath is set forth in Table Vl below.

lletort- Afttr Weight W Loss (Jfltplc I lluitl $2 Ls \7 es 2 ii i: h U to t-s iii 2 '7,

\ i L.\ no at M4 "t It can be seen from the above data that the weight loss of the Etample I fluid is much smaller than that of the standard Y or ZY fluids.

Another sample of Example 2 fluid was taken and its flash point. fire point and autogenous ignition tempera ture was determined These values were also determined for standard Y and ZY fluids. The values ob tained are recorded in Table IV below.

It can be seen that the flash point, fire point and au' togenous ignition temperature of the Example 2 fluid TABLE Vl OSMOTIC WATER ABSORPTlON Sample Before After Y 0 l5)? HOH Example 2 Fluid 004% HOH [1247i HOH It can be seen from these results that the water pickup for the standard Y fluid increases from 0v l5 percent to 3.03 percent, almost 20 times as much. whereas the water pick-up of the Example 2 fluid increases from 0.04 percent to 0.24 percent or only 6 times as much. Thus. these results clearly indicate that the polysiloxane brake fluids of the present caseare only slightly hygroscopic and that they will pick up at most only 0.5 weight per cent water from the atmosphere even under excessive humid conditions or through osmosis. Since the polysiloxane brake fluid of the present case is fully compatible with up to 0.5 percent weight of water, this amount of water does not cause any difficulties. However, the brake fluids of the prior art can pick up from as much as ll percent water from the atmosphere under humid conditions.

EXAMPLE 8 The brake fluid of Example 2 was subjected to the tests set forth above in the specification for motor vehicle brake fluids. The results obtained from these tests as compared with the highest suggested specifications for brake fluids are set forth in Table Vll below:

li iitl TABLE VII Test Data for Example 2 Fluid Suggested Example 2 Test Spec. Fluid E.R.B.P. 446F 500F Wet E.R.B.P. 320 324 Flash Point 2l2 350 Viscosity l-40Ci I 800 667 Viscosity (100C) l.5 cc 5.5 cc Test DOT-4 Example 2 Spec. Fluid pH 7-H 7.2 High Temperature A3.0C Negligible Stability Chemical Stability A3.0C Negligible Corrosion ta) Metal wt. loss .2 mg Steel 0.0l5 mg tApprox.) .l mg Alumi- 0.007 mg num .4 mg Brass. 0.154 mg Copper lb) Appearance No Gelling No Gelling (c) Low Temperature No Gelling No Gelling at 23 i 5C (dJ Deposits None None (e) Sediment 0.1% 0.05% (f) pH 7-l l 7-ll (g) Rubber Hardness l5 IRHD l5 (hj Rubber Swell 0.55" 0.025" Fluid Appearance at Low Temperature (a) Clarity Clear Clear th] Crystals None None (c) Flow at 40C l l0 Evaporation 1%) 80% Residue Non-abrasive None Residue Flow Pt. 5C SC Corrosion Test Passed Oxidation Test Passed Stroking Properties Test Passed As can be seen from the test results, the Example 2 brake fluid met the highest requirements and specifications for brake fluid.

What I claim is:

l. A process for transmitting force in a hydraulic brake system of a vehicle having activating means. activated means, master reservoir means, and hydraulic line means connecting said activating means, said activated means and said reservoir means comprising applying mechanical force to said activating means wherein said activating means. said activated means, said master reservoir means and said hydraulic line means are substantially filled with a polysiloxane polymer having a structure,

where R is a monovalent hydrocarbon radical or a halogenated monovalent hydrocarbon radical, R is a divalent hydrocarbon radical, E is selected from the group consisting of where R is a polyvalent hydrocarbon radical having s number of hydroxyl groups, where s varies from 2 to 5. n is a whole number that varies from 2 to 4 and z varies from l to 4, where a varies from L] l to 2.02, b varies from 0.023 to 1.00 and the sum ofa plus b varies from 2.024 to 3.00.

2. The process ofclaim 1 wherein R is selected from alkylene and arylene radicals of up to 20 carbon atoms and R is an alkyl radical.

3. The process of claim 1 wherein a varies from 1.23 to 2.05, b varies from 0.055 to 0.92 and the sum of a+b varies from 2.074 to 2.5.

4. The process of claim 1 wherein the polymer has the structure,

atsiotrtsioi xtmsio siat 

1. A PROCESS FOR TRANSMITTING FORCE IN A HYDRAULIC BRAKE SYSTEM OF A VEHICLE HAVING ACTIVATING MEANS, ACTIVATED MEANS, MASTER RESERVOIR MEANS, AND HYDRAULIC LINE MEANS CONNECTING SAID ACTIVATING MEANS, SAID ACTIVATED MEANS AND SAID RESERVOIR MEANS COMPRISING APPLYING MECHANICAL FORCE TO SAID ACTIVATING MEANS WHEREIN SAID ACTIVATING MEANS, SAID ACTIVATED MEANS, SAID MASTER RESERVOIR MEANS AND SAID HYDRAULIC LINE MEANS ARE SUBSTANTIALLY FILLED WITH A POLYSILOXANE POLYMER HAVING A STRUCTURE,
 2. The process of claim 1 wherein R'' is selected from alkylene and arylene radicals of up to 20 carbon atoms and R is an alkyl radical.
 3. The process of claim 1 wherein a varies from 1.23 to 2.05, b varies from 0.055 to 0.92 and the sum of a+b varies from 2.074 to 2.5.
 4. The process of claim 1 wherein the polymer has the structure,
 5. The process of claim 4 wherein the polymer has the formula,
 6. The process of claim 4 wherein the polymer has the formula, 